Green and sustainable chemistry in practice: Development and industrialization of a novel process for polycarbonate production from CO2 without using phosgene

This review focuses on the world's first process succeeded in development and industrialization by Asahi Kasei Corp. for producing an aromatic polycarbonate (PC) using CO2 as starting material.(1) The carbonate group of PC links directly to the residual aromatic groups of the bisphenol. Until Asahi Kasei's new process is revealed, all of carbonate groups of PC in the world were derived from CO as starting material. Furthermore, more than about 90% of PC has been produced by so-called phosgene process, and the PC contains Cl-impurities. It needs to use not only highly toxic and corrosive phosgene made from CO and Cl-2 as a monomer, but also very large amounts of CH2Cl2 and water, and needs to clean a large amount of waste water. The new process enables high-yield production of the two products, Cl-free and high-quality PC and high-purity monoethylene glycol (MEG), starting from ethylene oxide (EO), by-produced CO2 and bisphenol-A. PC produced by the new process has many excellent properties compared with conventional PCs. The new process not only overcomes drawbacks in the conventional processes, but also achieves resource and energy conservation. The reduction of CO2 emissions (0.173 t/PC 1 t) is also achieved in the new process, because all CO2 is utilized as the component consisting main chains of the products. The newly constructed commercial plant of Chimei-Asahi Corp. (Taiwan), a joint venture between Asahi Kasei Corp. and Chi Mei Corp., has been successfully operating at full-production since June 2002. The initial capacity (PC:50,000 t/y) is now increased to 150,000 t/y. A typical example of the Green and Sustainable Chemistry (GSC) contributing to society and mankind has been realized.